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Frame & Firewall Massaging:

Notching out the Forward Frame Cross-Member

 

With our original thought of mounting the engine as low as possible this was one of our first steps; it was clear it needed to be done.?.?  Again, in hindsight, with the engine sitting as high as possible, we may have been able to cut a smaller notch in that cross-member, but I think it still needed some relief.

It was straight forward enough and we elected to delay welding it up until we were done most of the other fitment.

 

Resting the oil pan on a small piece of 1/2" plywood on the cut portion helped secure the Engine and Transmission assembly in a position very close to what we thought would be the final position helped greatly whicle fabricating the Engine Mounts.

 

Later we just added two pieces of angled steel and some quick caps to close it all in.  We did make the angled steel as long as possible but still able to fit in and slide to a centered position before welding.

 

Clutch

 

To date I haven't seen a Miata build that used ALL of the Miata Clutch components.  The only things I've seen are hybrids, either Miata Master with Spit Slave, Miata Slave with Spit Master, or even both from the original Spit.  To me there was no decision here, it all had to be Japanese.

 

The Master Cylinder, although not difficult to implement will take some more description so I will leave that until later.

Clutch Slave

 

Very Important - As mentioned in my general notes, I believe there are better ways to fit a Clutch Slave so I will first address those and then what we did.

 

 

 

 

 

 

 

 

 

 

 

 

 

The Miata Clutch is very light, especially compared with our Spitfire's.

 

I think a BETTER option to cutting out that much of the frame rail would have been to shorten the Clutch Lever by an inch or so and adjust the geometry of the Slave Cylinder housing, or better yet where it attaches to the Bell Housing.

 

The Clutch Lever that sticks out of the Bell Housing and activates the Throw Out Bearing is constructed of fairly thick stamped steel with a cupped area to receive the end of the Activation Rod from the Slave Cylinder.  Modifying this to be an inch or so shorter would be very straight forward and although the rubber grommet may need to be trimmed back I think it would work nicely.

 

The more difficult part of the process would be the requirement to re-aligning the Slave Cylinder to similar geometry as the factory set-up so it doesn't pop out of that recess or impart any lateral force on the Slave Piston.  My preference would be to modify, perhaps by shaving down the flat surface, of the Bell Housing threaded hole portion, to allow use of a totally stock Slave Cylinder in the event of replacement later.

However, modifying the Slave would be easier and likely more practical.

Perhaps a combination of modifying the flat part of the block the Slave rests up against and the Slave housing as well?

 

To me it seems the BEST solution would have been a Hydraulic Throw-Out Bearing, fully contained inside the Bell Housing; I suspect this may have meant NO alterations to the frame at that location.

 

I've never heard of anyone using one of these on a Spitfire / Miata so it may take some research to determining which one to purchase.

 

Benefits are obvious, however, some of the detractors would include....

  • Cost,

  • New concept fitment,

  • Uncertain durability, and of course,

  • Replacement requires separating the Engine and Transmission.

 

I always come up with these great ideas after the fact!!!...

Hopefully someone else can report back on these and any other options.

Frame Relief for Clutch Slave - What we did...

 

The drawbacks to cutting the frame at this point are obvious, however, the benefits to how we did this are...

  • Uses completely stock, unmodified Miata pieces,

  • Cost very little,

  • Is a proven Clutch System, and

  • Required only pieces we already had on hand so no time delays researching and ordering.

 

We removed the Clutch Slave Cylinder early on for easier test fittings knowing that was an area we would eventually cut.  Once engine/transmission geometry was correct we started on it.

 

Because that area is right on a curved portion of the frame rail we were especially careful to reinforce it well.
I'd admit that none of my welding is pretty, but it's definitely strong.

 

After relieving the least amount of original frame we felt necessary, I cut and bent (just using a hammer on it over a piece of 2-by wood) a piece of 1/4" steel to fit the curve of the box frame on the outside of the inner vertical and welded it in place.  (1/4” is overkill by the way; yes.... Klaus told-me-so! :) )

 

Next we reinforced the top and outboard vertical part of the box frame.  We did this on the inside of the box with a piece of 3/16” steel to which we added a 90 degree portion so it would weld to both the top and outside vertical of the inside of the box frame.

The complex-curve for the 3/16” plate to bring it all together took a bit longer to bend, twist, and bash into shape; consequently it had slightly less overhang than I'd planned, but again, plenty strong.

 

We also trimmed a tiny bit off the end of the Clutch Release Lever and re-welded a ridge on it.  Every millimeter is sacred.

As an aside... Although I'd much prefer non-destructive testing and, I'd rather not share all of my stupidity, this bit is worth-while...  My buddy Mark and I did some impromptu and quite unintentional strength-testing of that frame modification...  On the very first AutoCross I attended with the Miata set-up I went slightly off-line and managed to go over a significant undulation in the pavement at a decent speed!  With the pair of us together weighing in just shy of 400 pounds I was mortified during the teeth-shattering event!  The front suspension bottomed out and although I was certain even an unmodified Spitfire would have folded in the middle, we were very pleased to see that everything remained straight.  Dohhh!  But at least there is no concern of frame strength!

Firewall

 

Continued trimming the firewall to get things to slide back nicely.  Also mucked about with some metal to fill the gap between the battery box and tub as well as a surface to secure the Tunnel Cover that will eventually have to be custom made.

Longitudinal Frame Rails Outboard of Transmission

 

We did some minor shaving of the frame overhang at various places, but only millimeters.

Short Frame Cross-Member Aft of Transmission

 

Initial fitment showed the requirement to notch out part of the small cross member to make room for a small supporting ridge on the underside of the Transmission Output Shaft Housing so we cut out just a bit.

In the end with our slightly higher Transmission position, I'm not certain this was required but what's done is done.  Later I welded in a small cover.

Engine Block - Alternator Removal Assistance Tab (that's a fancy name I think Mazda should use!)

 

The Miata engine block has a very cool little tab cast into it under the alternator mount allowing one to insert a screw driver and easily pry the alternator from its mount - very slick especially in the confined space of the Miata engine compartment.  Unfortunately at that point of fitment we felt we would need more room to clear the Turret so we shaved it off; no big deal really as in the Spitfire there is ample room to access and manipulate the alternator out anyway, but I just hate cutting out useful bits.  If I ever have a do-over, and I may, I would leave it there until the very end to make that decision.

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